1. Field of the Invention
The present invention is for a system for the chemical analysis of gases which are potential atmospheric pollutants.
2. State of the Art
The determination of the concentration of organic chemicals in a gaseous sample is important in the control of air pollution. Many industries generate large quantities of gaseous organic compounds which are discharged into the atmospheres. While in the atmosphere the organic substances often undergo complex chemical interactions to produce chemicals collectively known as photochemical smog. The exact nature of all the chemical interactions involved in the production of photochemical smog is presently unknown. However, it is believed that methane, CH.sub.4, is not involved in the production of photochemical smog.
In order to reduce the production of photochemical smog, regulatory agencies such as the U.S. Environmental Protection Agency place limitations upon the amounts of organic chemcials which may be emitted into the atmosphere by industries. Such regulation requires monitoring of the organic emissions from the industries. Since it is believed that most, if not all, organic chemicals, with the important exception of methane, are involved in the production of photochemical smog, the analysis of organic emissions for organic chemicals other than methane is important. The chemicals which should be analyzed for are collectively known as total gaseous nonmethane organic chemicals (TGNMO). However, there is presently no analyzer for TGNMO which is satisfactory in terms of being simple and easy to use and giving accurate results.
There are known methods and systems for analyzing samples of gases to determine the concentration of volatile organic compounds therein. For example, U.S. Pat. No. 4,003,257 teaches a system for analyzing volatile organic compounds by gas chromatography. According to the patent, a gaseous sample is passed through a sample trap which contains an absorbent material such as a polymer of 2,6-diphenyl-p-phenylene oxide (PPPO) sold commercially under the registered trademark Tenax GC. As the sample flows through the sample trap, volatile organic compounds are absorbed on the absorbent while other compounds pass through and are vented to the atmosphere. After this step of absorption has been completed, the sample trap is coupled to a gas chromatograph, and a carrier gas is transferred through the sample trap while the trap is heated. Thereby the absorbed volatile organics are desorbed into the carrier gas and the carrier gas, along with the volatile organics, is transferred to the gas chromatograph. In the gas chromatograph, the various organic compounds are separated and analyzed to determine the concentration of each compound.
This patented system includes a complex means for separating by gas chromatography the various constituents of the sample. Furthermore, the patented system is believed not to analyze for certain important organic chemicals including ethane and ethene, for example.